1. Field of the Invention
This invention relates to an optical printer used in an optical recording apparatus such as a stationary and portable printer, copying machine and so on. More particularly, this invention relates to an optical printer constructed so as to write to a recording medium by switching plural kinds of filters.
2. Description of the Invention
In general, the optical printer is provided with a light source comprising a number of delicate light emitting dots arranged linearly and is an apparatus for forming a desired image to the recording medium while moving the light source in the direction crossing at right angles the direction of arrangement of the emitting dots to irradiate the recording medium with dotted light. As the light source is used an elements based on a various kinds of principles of light emission, for example, a fluorescent light-emitting tube, LED and so on.
FIG. 13 is a schematic cross-sectional view showing an outline of the construction of an optical printer used in a conventional optical writing apparatus, for example, a portable color printer and so on. FIG. 14 is a plan view showing a print head a part of the construction of which is omitted used in the optical printer.
As shown in FIG. 13, the print head 100 used in the optical printer can move back and forth relative to sub-scanning direction to a film 102 as a recording medium located at a given position. That is to say, as shown in FIG. 14, the print head 100 is guided by a pair of guide shaft 104,104 parallel in the sub-scanning direction and further is connected with a wire 108 driven by a motor 106 to move back and forth in the sub-scanning direction. And, the print head 100 comprises a light emitting element (light source) 110 which has a plurality of light emitting dots arranged in the main scanning direction. The light from the light emitting element 110 passes through filters (R, G, B) as described after and forms an image on a film 102 via a reflecting optical element 112, a life-size optical system 114, a reflecting optical element 116.
As shown in FIG. 13, three filters R, G, and B of red (R), green (G) and blue (B) are located switchably on the side of the light emitting element 110 which is irradiated with light. As shown in FIG. 14, these three filters R, G and B have, respectively, a shape the longer direction of which is the main scanning direction and are arranged in the direction of sub-scanning and mounted to a common frame 118. The frame 118 is provided with a projection 120 for operating a frame. The projection 120 is retained by a guide bearing 122 and a positioning bearing 124. The positioning bearing 124 is forced by a spring 126 and engages with one of three notches formed in the projection 120. The frame 118 is forced by a spring 130 toward a given direction in the direction of sub-scanning. A stopper 132 is provided at a given position on the side of the projection 120 and a reset plate 134 is provided at a given position on the opposite side of the stopper 132 so as to interpose the optical writing head between the stopper 132 and the reset plate 120. That is to say, when the projection 120 of the frame 118 strikes against the stopper 132 with the movement of the print head 100, the frame 118 moves to change and the filters (R, G, B) are switched. And, when the optical writing head 100 moves in the direction opposite to the stopper 132 and the reset plate 134 moves a shaft 136 of the positioning bearing 124, the engagement of the frame 118 by the positioning bearing 124 is released and the frame 118 moves in the direction of the stopper 132 by the spring 130.
Next, a writing operation to the film 102 according to the aforementioned construction is described with reference to FIG. 15. FIG. 15 is a diagram in which the writing operation to the film at the aforementioned print head is illustrated sequentially according to the procedures shown by arrow marks. In FIG. 15, arrangements of longitudinal figures shown in (a), (b) and (c) show a filter reset action, an action from the start to the end of the exposure, and a switching action of the filters (R, G, B) after the exposure, respectively. In FIG. 15, a mark xcex94 of the light source 110 shows a position of the light emitting dot line. According to this optical writing head 100, an image is color-separated into three primary colors of R G B and a full color image is formed by writing an image of each color to a sheet of film one over the other.
As shown in FIG. 15(a), the reset plate 134 moves the shaft 136 of the positioning bearing 124 to the left with the movement of the optical writing head 100. The frame 118 moves to the right by the spring 130 and is reset at an initial position where the filter R is set at a position where the light emitting element 2 is irradiated with right (mark xcex94).
As shown in FIG. 15(b), the optical writing head 100 moves to the right along the direction of sub-scanning in FIG. 15(b). In synchronization with this, the light emitting element 100 is driven by an image signal of R (red). An image of R (red) is formed to the film.
As shown in FIG. 15(c), when the image of R (red) is formed to the film, the projection 120 of the frame 118 strikes against the stopper 132 at the right end in FIG. 15(c) and the frame 118 moves and the filter is switched from R (red) to G (green).
Thereafter, the optical writing head 100 moves to the starting position of exposure on the left side in FIG. 15(a) where reset of the filter is not performed because the reset plate 134 does not contact with the shaft 136 of the positioning bearing 124. And, similarly to the aforementioned (b), the optical writing head 100 moves to the right along the direction of sub-scanning in FIG. 15(b) and, in synchronization with this, the light emitting element 110 is driven by an image signal of G (green) to form an image of G (green) to the film. And, similarly to (c), the projection 120 of the frame 118 strikes against the stopper 132 at the right end in FIG. 15(c) to move the frame 118 and the filter is switched from G (green) to B (blue).
Thereafter, the optical writing head 100 moves to the starting position of exposure on the left side in FIG. 15(a) where reset of the filter is not performed because the reset plate 134 does not contact with the shaft 136 of the positioning bearing 124 by controlling a movement distance of the optical writing head. And, similarly to the aforementioned (b), the optical writing head 100 moves to the right along the direction of sub-scanning in FIG. 15(b) and, in synchronization with this, the light emitting element 110 is driven by an image signal of B (blue) to form an image of B (blue) to the film. And, similarly to (c), while the optical writing head 100 reaches the right end in FIG. 15(a), the filter does not move any more to the left because it has been switched to the extreme left side.
Thereafter the optical writing head 100 moves to the starting position of exposure at (a) on the left side in FIG. 15(a) and the reset plate 134 contacts with the positioning bearing 135 to perform the reset of the filter. Thereby, the filter is set again at R (red).
As above described, in the aforementioned conventional optical printer the optical writing head 100 can move in the direction of sub-scanning to the film 102 located at a given position. And, the optical writing head 100 is constructed so as to switch with moving action the plural kinds of filters (R, G, B) located movably in the direction of sub-scanning.
Accordingly, the aforementioned conventional optical printer requires wide space for moving the optical print head 100.
And, in case of the aforementioned conventional optical printer, the scanning should be performed repeatedly corresponding to the number of the filter (three filters R G B in the aforementioned example) and, therefore, an image can not be formed by one time exposure.
And, in the aforementioned conventional optical printer, the filters are switched by striking the head 100 against the stopper 132 with the action of the movement of the head 100, and on the opposite side the reset is performed by contacting the head 100 to the reset plate 134. Therefore, spatial room is required at both positions for the length obtained by subtracting the width of a sheet of filter from overall width within which the filter moves. That is to say, since three kinds of filters R, G, B are used in this example, spatial room two times and above width in the switching direction of one filter is required for switching and reset.
Further, when the aforementioned conventional optical printer is constructed so as to switch the filter by sliding, there occurs minute dust by a rub between a casing (frame 118) which contains the filter and guides the movement of the casing and the other members and the filter. There has been a disadvantage that the minute dust enters into a light path to cause optically an eclipse which is taken in the film.
And further, since the aforementioned slide-type switching filter has no choice to be located between the light source 110 and the reflecting optical element 112, there has been a disadvantage that the total thickens of the print head 100 is large.
This invention has its objective to solve the aforementioned disadvantages due to a mobile printer or a slide switchable filter.
An optical printer of this invention is characterized by comprising a light source which emits light, a rotatable optical member which is located in a light path between the aforementioned light source and a recording medium and which selects light having specific wavelength range from the aforementioned light source, a moving means for moving relatively the aforementioned light source or the aforementioned recording medium, and a controlling means for performing synchronously a light emission of the aforementioned light source by an image signal corresponding to the light having the specific wavelength range selected by the aforementioned optical member and rotation of the aforementioned optical member and for forming an image to the aforementioned recording medium by irradiation with light selected by the aforementioned optical member.